使用Servlet过滤器实现用户登录验证

public class LogOrNot implements javax.servlet.Filter {
private FilterConfig config;
private String logon_page;
private String home_page;
public void destroy() {
config = null;

}
public void init(FilterConfig filterconfig) throws ServletException {
// 从部署描述符中获取登录页面和首页的URI
config = filterconfig;
logon_page = filterconfig.getInitParameter("LOGON_URI");
home_page = filterconfig.getInitParameter("HOME_URI");
System.out.println(home_page);
if (null == logon_page || null == home_page) {
throw new ServletException("没有找到登录页面或主页");
}
}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse rpo = (HttpServletResponse) response;
javax.servlet.http.HttpSession session = req.getSession();

try {
req.setCharacterEncoding("utf-8");
} catch (Exception e1) {
e1.printStackTrace();
}
String userId = (String) session.getAttribute("UserId");
String request_uri = req.getRequestURI().toUpperCase();// 得到用户请求的URI
String ctxPath = req.getContextPath();// 得到web应用程序的上下文路径
String uri = request_uri.substring(ctxPath.length()); // 去除上下文路径，得到剩余部分的路径
try {
if (request_uri.indexOf("LOGIN.JSP") == -1 && request_uri.indexOf("LOG.JSP") == -1 && userId == null)
{
rpo.sendRedirect(home_page+logon_page);
System.out.print(home_page+logon_page);
return;
}

else {
chain.doFilter(request, response);
}
} catch (Exception e) {
e.printStackTrace();
}
}

}

Code Author:Jacy.